70 Hp Evenirude

[Just_2_b_me]

Hey guys thanks in advance,

Man where to start ! what a nightmare, I have a 76 carvelle trihull I bought last summer it came with a 1976 70 hp Johnson, well it ran alright for most of the summer then started giving me fits towards the end of the year so I put it in the shop a month back to get ready for summer and found out I have a cracked block.(water is getting into the number 3 cylinder) So I bought an old 1976 70 HP Evenrude and swaped them out. (I have lots of spare parts at least) Engine runs good sitting in the driveway with muffs on but dies once its in the water.
I suspect its a fuel prob (dirty carb maybe, but I did swap the ones off of my old motor and it helped, just not enough)(maybe a bad fuel pump?) also probably is needing sync but I can't keep it running long enough to adjust things.
But the cracked block is haunting me so I need another question answered as well and can't find a good answer in the Selco manual I bought.
There are two holes just below the engine cowling about the size of a dime, is water supposed to come out of these holes?

Agian thanks !!!

 

[jims3000]

Re: 70 Hp Evenirude

i believe it is to help relieve pressure when the foot is under the water and i also hear you can take a 1 inch drill bit and drill through the plate behind it and get a little better performance and better ideling when in water.the exhaust runs down behind the 2 holes and out the prop if you drill the holes out it will relieve alot of the exhaust pressure that has to go down through the foot.

 

[tashasdaddy]

Re: 70 Hp Evenirude

those are exhaust relief ports, for when idling, there is not enough pressure to push the exhaust out the prop exhaust. the engine runs on muffs, because there is no backpressure on the exhaust that there is in the water. the idle when tuned should be 650-700 in the water in gear, this means on muffs it should be idling around 800-850.

 

[F_R]

Re: 70 Hp Evenirude

Just wondering how you arrived at the cracked block diagnosis. Did you check for leaking head and exhaust cover gaskets?

Yes, water is supposed to blow out the exhaust relief holes.

 

[Just_2_b_me]

Re: 70 Hp Evinrude

Re: 70 Hp Evinrude

Thanks for the info, whew what a relief.

As for the cracked block, yes the boat shop I had taken it to originaly thought it was a blown gasket and changed it, but then noticed water coming out of a hairline crack behind the powerpack and susequently found it was still getting into the #3 cylinder, thats why I bought the other engine.

More info on the used engine I bought, (I bought it from a boat repair shop that had lost it's lease and was having to move so they were selling alot of old used outboards and parts so they didn't have to move/store them untill they got relocated) before buying it I had the mechanic (with me watching) do a compression test and a spark test. Compression was 120 +/- 2 psi on all three cylinders, and I appeared to be getting 3 good sparks.

So you folks think I'm on the right track suspecting fuel issues ?

 

[tashasdaddy]

Re: 70 Hp Evinrude

Re: 70 Hp Evinrude

yeah, time to look at the carbs, and get the jets out. if they are fixed you need FR's special tool to get them out. can be made from a quailty screw driver.
http://i155.photobucket.com/albums/s311/frankr_photos/FixedJetScrewdriver2.jpg?t=1177353186

 

[Just_2_b_me]

Re: 70 Hp Evenirude

Hey guys, just a quick update.

I rebuilt my original carbs, found the low speed jets to be clogged on two of them and the high speed one clogged on one as well. I also replaced all my fuel lines, also there were no keeper springs on any of the needle/float valves.

And those were my good carbs !

Oh my God the the old carbs that came on the used motor, someone had broken the the jets trying to get them out, I had to use an easy out and let them soak in penetrant for a while. what a mess they are ....

Anyway I took the kids camping/fishing this last weekend and the boat runs great !

Thanks to all of you !!